1. Field of the Invention
This invention relates to structural damage detection systems for structures in a borehole and, more particularly, to structural damage detection systems utilizing optical fibers.
2. Description of the Related Art
Exploration and production of hydrocarbons generally require a borehole be drilled into a geologic formation. Various structures may be called upon to be inserted into the borehole as part of the exploration and production. Examples of these structures include a borehole casing and a sand screen.
Due to instabilities in the formation such as reservoir compaction, the formation may exert a force on a downhole structure high enough to deform the structure. If the downhole structure is deformed, it is important to know the extent of the deformation. By having knowledge of the deformation, mitigating or corrective actions can be initiated.
One method to measure a deformation is to attach strain sensors to the downhole structure prior to the structure being placed in the borehole. Each strain sensor provides a measurement of the strain experienced by the structure at the location of the sensor. With enough sensors, it is possible to determine a deformation and therefore a shape of the downhole structure. Data from the sensors is processed using an algorithm to determine the deformation. However, depending on the number of sensors, locations of the sensors, and discontinuities in the data, it is possible for the algorithm not to converge on an accurate solution and, therefore, not determine the shape.
Therefore, what are needed are various techniques to accurately determine the shape of a structure downhole.